Sealing system for blast furnace bells for high pressure top operation



1965 N. B. MELCHER ET AL 3,221,906

SEALING SYSTEM FOR BLAST FURNACE BELLS FOR HIGH PRESSURE TOP OPERATION Filed Feb. 11, 1964 5 Sheets-Sheet 1 INVENTORS NORWOOD B. MELCHE'R WARREN M. MAI/AN z ATTORNEY N. B. MELCHER ET AL 3,221,906 SEALING SYSTEM FOR BLAST FURNACE BELLS FOR HIGH PRESSURE TOP OPERATION 3 Sheets-Sheet 2 Dec. 7, 1965 Filed Feb. 11, 1964 mm m m m am m Mm i D 4 w .A Wm

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United States Patent 3,221,906 SEALING SYSTEM FOR BLAST FURNACE BELLS FOR HIGH PRESSURE TOP ()PERATION Norwood B. Melcher, Minneapolis, Minn., and Warren M. Mahan, Bethel Park, Pa., assignors to the United States of America as represented by the Secretary of the Interior Filed Feb. 11, 1964, Ser. No. 343,902 5 Claims. (Cl. 214-36) (Granted under Title 35, US. Code (1952), sec. 266) The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

The present invention relates to improved blast furnace bell and hopper structures and a method for operating such structures. More particularly, it concerns apparatus made an integral part of bell and hopper structures which facilitates operation of a blast furnace at ultra high pressures, including top pressures as high as 40 p.s.i.g. The desirability of operating a blast furnace at a high top pressure is now well recognized in the art. Many advantages including low coke rate, low flue dust with decreased dust losses, lower gas cleaning cost, and higher iron production, can normally be expected to follow from high pressure operation. However, extended working of a blast furnace at the relatively higher pressures becomes economically feasible only when a tight gas seal between the furnace proper and the furnace top assembly can be maintained without frequent overhauls of the sealing means. A major contributing factor to lost furnace time when operating at high top pressure is the relatively short effective life of bells and bell hoppers due to the strong erosive action of the abrasive, hot dustladen gases escaping past such parts during the times they are separated for the repeated chargings of coke, ore and other materials regularly required for continuing The method and apparatus according to the present invention permits a tight seal between bell and hopper parts to be sustained even after prolonged furnace operation at high pressures.

Characterizing the principal features of the bell and hopper structures of the present invention are a special non-metallic to metal seal means, and further means to protect the non-metallic substance of the seal by cleaning and cooling the contacting surfaces of the seal means and surfaces adjacent thereto. A resilient non-metallic substance is preferred for this seal means to allow a tight closure to be effected in the event such substance may possibly contact a roughened surface. Cleaning the contacting surfaces is accomplished using gases under high pressure, and preferably cleaned blast furnace gases. Such gases are supplied at high pressure to a blow pipe structure, close by these contacting surfaces, which functions to blow jets of these gases directly upon the relevant bell surface whereby they sweep over the bell as it is being moved into place to close the hopper. Provision is made to cool the closure area by supplying circulating coolant to a conduit surrounding a portion of the hopper adjacent the closure area, although it is obvious that other cooling expedients may be used for this purpose.

It is therefore an object of the present invention to provide a method and means permitting use of high top pressures in blast furnace operations to be economical and efiicient.

Another object of the invention is to provide means for obtaining a tight seal for a bell and hopper structure functioning in a blast furnace operating at high top pressures.

A further object of the invention is to provide cleaning and cooling means, as an integral part of a blast furnace 3,221,906 Patented Dec. 7, 1965 ice bell and hopper structure, which allows such structure to continue to effectively seal the blast furnace even after extended operation thereof at high top pressures.

These and other objects of the present invention will be more clearly understood from the following description of a preferred embodiment of the invention considered together with the accompanying drawing wherein:

FIG. 1 is a schematic representation of some of the various basic structural components constituting the upper section of a blast furnace including bell and hopper arrangements according to the present invention;

FIG. 2A is a cross-sectional view of a portion of the improved bell and hopper structure represented in FIG. 1;

FIG. 2B is a fragmentary sectional view showing particular details of the structure represented in FIG. 2A; and

FIG. 3 is a chart on which are represented the sequential relationships between operations of the basic directing and controlling equipment essential to the performance of the bell and hopper structure according to the present invention.

In the schematic representation of FIG. 1, an upper portion of a blast furnace 10 may be seen to include a furnace stack 20 having vertically arranged over an upper opening therein a cylindrical shell 21. To the inner surface of shell 21 are attached three inverted truncated, conical shells 16, 17 and 18, in a superimposed relationship. Three generally conically shaped bells 22, 23 and 24, shown fitted within the lower circular openings in conical shells '16, 17 and 18, respectively, coact therewith to form separately operable bell and hopper structures which define an upper chamber 26 between bells 22 and 23, and a lower chamber 27 between bells 23 and 24. The top bell and hopper structure comprising conical shell 16 and bell 22, located close to the upper open end of cylindrical shell 21, is operative to provide a base for a compartment 28 constituting a receptacle to which charging materials for the blast furnace are initially supplied from a revolving chute 30. Charging materials are delivered to chute 30 by means of a skip-car or bucket arrangement depicted in FIG. 1 as a skip-car 31, whose operation is coordinated with that of the blast furnace bell and hopper structures in a manner well known in the art.

Appropriate vertical displacements of bells 22, 23 and 24 relative to the respective conical shells in which they function, are facilitated by -a conventional lever operated, nested shaft construction of the type disclosed in Patent No. 2,408,945, issued to Mohr, Jr., et al., on October 8, 1946. In FIG. 2A of the present disclosure this construction may be seen to comprise a shaft 32 passing through a tubular shaft 33 screwed into a fitting 34 fastened to the top of bell 23. Shaft 32 extends through a central opening in bell 23, and a bearing device 35 fixed therein, and thence into a fitting on bell 24 fixing the shaft thereto. Hopper 30 between skip 31 and the upper bell 22 is adapted to revolve whereby it facilitates the distribution of the charges uniformly into the furnace. Charging is accomplished at three positions of the revolving hopper during a dumping cycle. An initial dumping from the skip occurs with the revolving hopper stopped at a point followed by dumping with the revolving hopper stopped at the 240 point and at the 360 or 0 point. Charges are thereafter dumped in accordance with this pattern as required by furnace conditions and its operational schedule.

Bells 22, 23 and 24, as seen in FIG. 1, also comprise as integral parts of their respective base portions, short, cylindrical sections 33, 34 and 35. Fixed in position so as to be suspended closely adjacent to the base portions of each of the respective bells 22 and 23, is a blow pipe structure, indicated by numerals 36 and 37 in the drawing. As shown in FIGS. 2A and 2B, this structure is mainly comprised of a ring shaped tubular pipe 38, which is maintained in its suspended position with respect to hell 23 by supporting devices depending from a rim section 39 of the conical shell 17 associated with the bell. Comprising this pipe support structure is a circular flange 40 welded to an outer cylindrical surface 41 of rim 39, and a number of J-shaped hooks 44, bolted to flange 40 at suitably spaced points adjacent its outer peripheral edge. Pipe 38 is firmly held between hooks 44 and the underside of flange 40 so as to bear against a lower, outer edge of rim 39 whereby the bottom half of the pipe is situated below the lowest edge of the rim. Evenly spotted around the lower wall of pipe 38 which faces bell 23, are approximately 100 relatively small radial passages 48 opening into the pipe. These passages are downwardly disposed so as to align their openings approximately parallel to the incline of the bells conical surface 50. As will be hereinafter fully explained, this construction allows gases under pressure discharge from passages 48, to impinge directly upon surface 50 of the bell when it is rising from a position of any appreciable distance from the closed phase thereof shown in FIGS. 1 and 2A.

As was hereinbefore indicated, operation of a blast furnace at high top pressures can be satisfactorily accomplished only when an effective seal is obtained between the bell and hopper elements of the furnace following any furnace charging procedures. According to the present invention, a requisite positive seal is gained for its bell and hopper structures with means characterized by a non-metallic to metallic contact between the sealing parts thereof. Although accomplishing this positive seal for the middle bell and hopper elements 23 and 17, is essentially the key to successful high top pressure operation, preferred operation requires that the upper bell and hopper elements 22 and 16, as well as these middle elements be equipped to effect the non-metallic to metallic seal. However, the stack bell and hopper elements 24 and 18, being in the hottest area of the bell and hopper system, operate to effect only a metal to metal seal by their closure.

With reference to FIGS. 2A and 2B, it may be seen that a construction comprising the sealing parts for the middle or intermediate bell and hopper elements 23 and 17, includes a keying mortised groove 60, circumscribing the middle of a lower inner conical surface 61 of rim 39, and sloped to parallel the inclined conical surface 50 of bell 23, and a gasket 62, of non-metallic, resilient material, shaped to fit into the key of groove 60. The gasket 62 is securely retained in groove 60 by a suitable adhesive, such that a relatively short portion of the gasket extends outside rim 39. As is evident from the showing in FIG. 2B, this extended portion of the gasket is compressible by the bells conical surface 50, as it rises to effect a closure of the bell and hopper structure. Various resilient materials capable of withstanding temperatures above 250 F. can be used for the sealing gasket. An applicable sealing substance is a silicon rubber composition such as the General Electric, general purpose class 400 silicone rubber materials whose physical properties are a hardness of 401-5 durometer, a tensile strength of 700 p.s.i. and above, a 240 percent elongation, a 25 percent maximum compression set at 300 F. for 70 hours, and effectiveness in a 80 F. to +500 F. temperature range. A General Electric extreme high temperature class 700 silicone rubber material may also be fabricated into a suitable sealing gasket.

To aid the maintenance of a favorable temperature about the sealing gasket 62, provision is made to cool rim 39 -by circulating coolant around the outer wall of the rim. For this purpose a tube 65 of copper, or like good heat transfer material, is flattened to provide a wide heat transfer surface which is secured by welding, or the like, to outer cylindrical surface 41 of rim 39, and to the support flange 40 fixed to this cylindrical surface. Tubing of suflicient length is provided to completely encircle the surface 41, and inlet and outlet coolant connections are made thereto through the enclosure about the bell and hopper structure in a manner well known in the art. As is schematically shown in FIG. 1, upper bell and hopper elements 22 and 16, also have cooperatively as sociated therewith a tube 68 for carrying coolant to protect their resilient sealing gasket (not shown), in addition to the blow pipe structure 36, appropriately located by its attachment to a support flange on the hopper shell 16, to allow gases under pressure to pass from a pipe 69 to impinge upon the conical surface of bell 22.

As is now readily apparent from the previous explanations, the blow pipes 38 and 69 must function in conjunction with the operational control for vertically dis placing the bells associated therewith to assure that the metallic surface of each such bell is clean of charging materials before that surface contacts the non-metallic sealing gasket in the rim of the hopper shell related thereto. Moreover, this operational control for the bells is also coordinated with instrumentalities controlling pressure equalization in the bell and hopper chamber 26 and 27, and means operative to determine the height of the burden in the blast furnace proper. Since the gases jetted from the blow pipes for dispersing charging materials tending to adhere to the bells are preferably derived from gases normally available from blast furnace operation, such gases must be suitably conditioned before they can be used as indicated. Exemplifying the gases supplied for use in the blow pipes are gases which have been cleaned to a residual dust content of .005 grain per standard cubic foot, at 0 p.s.i.g. and 125 F., and saturated with water vapor, and subsequently compressed to 100 p.s.i.g. and 100 F. The blast furnace gases thusly processed are supplied from a compressor to a pressure receiver from which they are released to effectuate the pressure equalization procedures, hereinbefore noted, as well as the cleaning of the bells surfaces by means of the blow pipes.

A requisite control for the aforesaid coordinated operational functions is obtained in the present invention by a system of valves, generally indicated by numeral 70 in FIG. 1, through which the conditioned gases must flow before they can become effective in the blast furnace top enclosure 21. Included among the valves of system 70 are blow pipe control valves 72 and 73, equalizer valves 75 and 76, relief valves 78 and 79, and pop safety valves 82 and 83. Additionally provided are vertically displaceable test rods 86 and 87, shown in FIG. 1 as projecting through the top of furnace 20 to sense the height of charging material or burden therein, whose operational requirements are interrelated with those involving the valves of system 70. The valve structures of system 70 may have any one of a number of conventional forms including the rack and pinion type disclosed in FIG. 4 of the aforementioned Mohr, Jr., et al. patent. Such valves may also comprise solenoid operated plugs or eccentric plugs which are actuated by cranks driven by a motor through suitable linkages moving between cam type limit switches. Test rods 86 and 87 may also take different forms including those in the nature of that shown in Patent No. 2,426,347 issued to W. M. Fulton on August 26, 1947, and PatentNo. 3,014,603 issued to H. Taubmann on December 26, 1961.

Referring once more to FIG. 1, it will be seen that the valves of system 70, shown at the right side of the figure, are operative in conduits to which the conditioned blast furnace gases are fed from their pressure receiver, and the valves shown at the left side of the figure are operative in conduits through which gases in the enclosure 21 are discharged to atmosphere. More particularly, a conduit 90 is provided from which gases at p.s.i.g. flow into parallel conduits 91 and 92 wherein blow pipe control valves 72 and 73, respectively, are operative. A

further conduit 95 is provided from which gases at pressures ranging from 4 to 44 p.s.i.g., to correspond to that in the furnace top structure, flow into parallel conduits 96 and 97 in which the pressure equalizer control valves 75 and 76, respectively, are operative. Conventional throttle valves 98, 98a, 98b and 98c, precede the control valves in each of the conduits 91, 92, 96 and 97, to permit field adjustments of the related gas fiows to be made as needed. Relief valves 78 and 79, along with pop safety valves 82 and 83, are separately operable in respective individual conduits connected in parallel to join a main conduit 99, opening to atmosphere.

In operation, chamber 26 between bells 22 and 23 is pressurized whenever bell 22 is in its closed position and is depressurized to allow bell 22 to drop its charge onto bell 23. Valve 78 is made operative to depressurize the chamber. Operating pressure is maintained at all times in chamber 27 between bells 23 and 24. However, to keep chamber 27 cool, a new supply of the pressurized gas is put into this chamber according to a schedule for the operations, to be hereinafter more fully explained, and the hot gas is removed through valve 79. Safety valves 82 and 83 are provided to operate in case excess pressure builds up in a chamber.

As was previously described, the control valves of system 70, in cooperation with test rods 86 and 87, achieve a sequential operation which is coordinated with the functions of the bell and hopper structures. Referring now to the chart of FIG. 3, on which are represented details of several such sequences of coordinated operations, there will be found listed in the charts left-hand column the devices relevant to the functioning of the blast furnace top structures, and marked across the top line of the chart a time scale in seconds to which the functions of these devices are related. Appropriate furnace charging programming equipment is provided to regulate and coordinate the sequences as set forth in the chart, and to interlock these charging operations in a forced sequence such that the charging of the furnace must proceed as indicated or the operations will be halted. Equipment of this type includes various control and limit switches in energizing circuits of electrically operated actuator means for the valves, rods, bell drives, etc., wherein such switches are arranged to be worked by a timed programmer apparatus. Various kinds of conventional control sequencing devices are adaptable for use in such apparatus. Among such devices are a timed revolving drum perforated to receive switch actuator pins selectively positioned thereon in a predetermined manner, and a magnetic storage drum or tape having a plurality of tracks on which switch operate control signals are selectively recorded.

For the purposes of the present disclosure, it can be assumed that conditions at the start of the charted operations are as follows:

An ore load and a coke load are on bell 24.

An ore load on bell 23.

No load on bell 22.

Pressures in hopper chambers 26 and 27 are equalized to the pressure within the furnace.

Equalizer valves 75 and 76 are open.

Relief valves 78 and 79 are closed.

Test rods 86 and 87 are on the furnace burden.

A coke skip 31 is loaded in the pit.

Chute 30 is positioned at 0.

If the test rods 86 and 87 sense that the burden of the furnace is low enough to take another charge, the actuation of a skip up control button will start the hoisting of the skip car loaded with coke. As the skip car leaves the pit and moves upwardly to deposit coke into compartment 28, the test rods are withdrawn from the furnace, and chute 30 revolves moving to the 120 position, all of which is indicated on the chart between time units 0 to 30. Once the test rods are withdrawn, bell 24 moves downwardly to open hopper 18, and remains down for a predetermined interval of time wherein the ore and coke loaded thereon is charged into the furnace. Thereafter bell 24 rises to close its hopper, as indicated on the chart between time units 25 and 29. As soon as bell 24 effects a closure, test rods 86 and 87 are again lowered to the burden, while bell 23 moves down to open hopper 17 and deliver an ore load to chamber 27. When bell 23 completes its downward course, the equalizer valves 75 and 76 are both operated to close. Once valve 76 is closed, relief valve 79 will open. Bell 23 remains down for a predetermined interval of time after which it starts to move up. However, as indicated on the chart between time units 40 and 45, when bell 23 starts up to close hopper 17, the blow pipe control valve 73 opens and remains open for the interval during which the bell rises.

As a result, gases under 100 p.s.i.g. pressure are steadily released from the passages 48 in blow pipe 38, and jetted against the conical surface of hell 23, until the bell surface is brought into contact with the resilient gasket 62 in the rim of the hopper shell.

Closure of hopper 17 by bell 23, and control valve 73 therewith, are followed by the opening of equalizer valve 76. When reaching open position, valve 76 initiates the operation of a timer for a predetermined interval at the end of which a control is activated to close relief valve 79. Further, if the skip car has reached the dumping position at the top of the furnace, and the dump time interval has expired, relief valve 78 will open. In the event relief valve 78 does open, bell 22 starts to move down opening the upper hopper to allow delivery of a coke load to chamber 26. After reaching its full down position, bell 22 remains lowered for a predetermined interval of time before it again rises to close its hopper. However, as is made evident by the sequence chart of FIG. 3, between time units 61 and 66, blow pipe control valve 72 opens as bell 22 starts to rise and remains open until closure of hopper 16 is approximately completed, whereby the conical surface of the bell is cleaned of charge particles and gas dust by gases issuing from blow pipe 69, under high pressure. As soon as valve 72 closes contemporaneously with bell 22, the equalizer valve 75 will open, and when valve 75 reaches its open position a timer is made operable for a predetermined period at the end of which relief valve 78 will close. Upon closure of valve 78, bell 23 starts to move downwardly to open hopper 17 and allow delivery of the coke load to chamber 27. As soon as this hopper is opened equalizer valves 75 and 76 are both closed, and upon closure of valve 76, the relief valve 79 is opened.

Bell 23 remains down to maintain its hopper open for a predetermined time interval, and thereafter starts to rise. As bell 23 rises, blow pipe control valve 73 opens to effect the cleaning of bell 23 in a manner hereinbefore explained, whereupon valve 73 closes as the hopper is closed by the bell. Equalizer valve 75, along with equalizer valve 76 open following closure of the hopper, and when valve 76 reaches its open position, a timer operates for a predetermined time interval at the end of which relief valve 79 closes.

At the end of the operational sequence involving the first skip load, the following conditions prevail:

Ore and coke loads are on bell 24.

No load on bell 23.

No load on bell 22.

Pressure in hopper chambers 26 and 27 are equalized to match the pressure in the furnace.

The equalizer valves are open.

The relief valves are closed.

The test rods are down to sense the height of burden.

A loaded ore skip is in the pit.

Chute 30 remains positioned at Operations again commence as the skip car of ore starts to hoist to the dumping position at the top of the furnace. After a predetermined dump time, which starts when the car reaches the dumping position, the equalizer valve 75 closes. In the sequence of operations which follows, the relief valve 78 opens, and the lowering of bell 22 is initiated to open hopper 16. After a predetermined interval of time, bell 22 moves up to close its hopper while blow pipe control valve 72 is open to effectuate a cleaning of the bells surface. The control valve 72 closes as the bell 22 closes its hopper, whereupon equalizer valve 75 starts to open. After valve 75 reaches an open position, a predetermined time interval elapses before relief valve 78 closes. Subsequent activations of the bells, valves, test rods, etc., thereafter continue in substantially the same sequences hereinbefore set forth.

It should be evident that the operational sequences previously described, are only illustrative of a pattern upon which can be based almost all other regular charging operations for a blast furnace. For example, in any continuous charging operations for the blast furnace according to this pattern, the several predetermined time intervals noted therein can be varied by suitable adjustments of the related programming equipment to conform to any specified operational requirements. As was previously indicated, there are many different forms of such programming equipment known to the art, that can be adapted to govern the timed sequencing of the coordinated control for the various valves, bells, test rods, skip car and chute, with which the present invention is concerned. Nevertheless, the particular type of equipment actually used for regulating the operational sequences does not constitute any significant part of the invention.

While preferred forms of the method and physical embodiment of the invention have been illustrated and described herein, it is understood that the invention is not liimted thereby, but is susceptible to change in form and detail.

What is claimed is:

1. In a blast furnace charging apparatus having bell and hopper devices, means intermittently operative to displace a bell of said devices between opened and closed positions with respect to a hopper cooperatively related therewith, and mechanisms to clean a surface of said bell, said mechanisms comprising a conduit having a multitude of passages directed outwardly therefrom, elements supporting said conduit on said hopper whereby said multitude of passages of said conduit have their outer openings facing the surface of said bell designed to contact said hopper when it is closed thereby, supply lines for furnishing a gaseous stream under pressure to said conduit, control valve means in said supply lines operable to disrupt or continue the flow of said gaseous stream therein to said conduit, and operation coordinating means responsive to said bell displacing means to regulate the operation of said control valve whereby the fiow of a gaseous stream under pressure is maintained in said supply lines and released to said conduit during the time said bell is displaced from an opened to a closed position with respect to said hopper such that said gaseous stream is jetted out of said multitude of passages and on to said hopper contacting surface of said bell.

2. The blast furnace charging apparatus of claim 1, wherein the said devices include a plurality of interdependently controlled and separately operable bell and hopper structures, each of said structures having individual means operable to displace the bell thereof between opened and closed positions with respect to the hopper cooperatively associated therewith, several of said plurality of structures each having cooperatively associated therewith an individual one of said mechanisms to clean a bell surface wherein the respective valve means of said individual mechanisms are separately operable to control the gaseous flow to the conduit operatively connected thereto, said operation coordinating means being responsive to the operation of each of said individual bell displacing means to separately regulate the operation of the said respective control valves whereby the gaseous stream jetted out of said multitude of passages of any conduit impinges upon the hopper contacting surface of the appertaining bell.

3. The blast furnace charging apparatus of claim 1 wherein a sealing means is effective to maintain a pressure tight closure between said bell and hopper of said devices when said bell is in closed position with respect to said hopper, said hopper comprising a rim portion having a surface thereon substantially parallel to said surface of said bell designed to contact the hopper, a groove in said rim surface, and a relatively heat resistant resilient gasket securely retained in said groove and having a portion thereof extending outside said groove, whereby said extending portion is compressed by said contacting surface of said bell when the latter is in said closed position with respect to said hopper.

4. The blast furnace charging apparatus of claim 3 wherein said rim comprised by said hopper includes an outer surface adjacent said conduit, said elements supporting said conduit on the hopper being dependent from the said outer surface, and a duct afiixed to said outer surface and adjacent to said supporting elements, carrying a coolant circulating therein for protecting the said gasket in the rim from adverse heating effects.

5. The blast furnace apparatus of claim 1 wherein the said conduit comprises a closed ring of tubular pipe and substantially all of said multitude of passages therein are evenly spaced along an inner wall of said pipe and directed toward a common point on the axis of the ring defining the shape of said vessel.

References Cited by the Examiner UNITED STATES PATENTS 2,477,406 7/ 1949 Church 21435 2,599,334 6/1952 Latham 214-36 2,765,935 10/1956 Schuman 21436 3,152,703 10/1964 Slagley 214-37 GERALD M. FORLENZA, Primary Examiner.

HUGO. O. SCHULZ, Examiner. 

1. IN A BLAST FURNACE CHARGING APPARATUS HAVING BELL AND HOPPER DEVICES, MEANS INTERMITTENTLY OPERATIVE TO DISPLACE A BELL OF SAID DEVICES BETWEEN OPENED AND CLOSED POSITIONS WITH RESPECT TO A HOPPER COOPERATIVELY RELATED THEREWITH, AND MECHANISMS TO CLEAN A SURFACE OF SAID BELL, SAID MECHANISMS COMPRISING A CONDUIT HAVING A MULTITUDE OF PASSAGES DIRECTED OUTWARDLY THEREFROM, ELEMENTS SUPPORTING SAID CONDUIT ON SAID HOPPER WHEREBY SAID MULTITUDE OF PASSAGES OF SAID CONDUIT HAVE THEIR OUTER OPENINGS FACING THE SURFACE OF SAID BELL DESIGNED TO CONTACT SAID HOPPER WHEN IT IS CLOSED THEREBY, SUPPLY LINES FOR FURNISHING A GASEOUS STREAM UNDER PRESSURE TO SAID CONDUIT, CONTROL VALVE MEANS IN SAID SUPPLY LINES OPERABLE TO DISRUPT OR CONTINUE THE FLOW OF SAID GASEOUS STREAM THEREIN TO SAID CONDUIT, AND OPERATION COORDINATING MEANS RESPONSIVE TO SAID BELL DISPLACING MEANS TO REGULATE THE OPERATION OF SAID CONTROL VALVE WHEREBY THE FLOW OF A GASEOUS STREAM UNDER PRESSURE IS MAINTAINED IN SAID SUPPLY LINES AND RELEASED TO SAID CONDUIT DURING THE TIME SAID BELL IS DISPLACED FROM AN OPENED TO A CLOSED POSITION WITH RESPECT TO SAID HOPPER SUCH THAT SAID GASEOUS STREAM IS JETTED OUT OF SAID MULTITUDE OF PASSAGES AND ON TO SAID HOPPER CONTACTING SURFACE OF SAID BELL. 